YCC? YCY? 와이씨 +17% Sparks HBM Rally, KOSPI +1.79%, Why?

This is not a 30-year marathon, but the intraday session is clearly a rally.

Data timestamp 2026-09-23 14:30 KST for intraday indices.

KOSPI: 7,143.71 (+1.79%) [2026-09-23 intraday(unconfirmed)]

KOSDAQ: 841.35 (+0.84%) [2026-09-23 intraday(unconfirmed)]

Retail investors ask, "Why is this rising so much, can I get in?" which is a common question.

We should sort reasons first, because numbers and news are lifting the market together.

What role does US IT and semiconductors play for the Korean market? (Source: signal bundle)

US IT and semiconductors: +5.74% (recent signal)

The rally in large US AI and semiconductor names provides a channel for funds to move into domestic semiconductor-related stocks.

Glossary note → HBM: high bandwidth memory, a semiconductor component with strong demand in AI data centers.

Why are HBM-related names jumping again? (Source: signal bundle)

Y씨: +17% (news headline)

D아이: +14% (news headline)

The surge in HBM names links AI data center demand expectations with rallies on foreign markets.

What catalytic effect does Apple news have? (Source: signal bundle)

Apple: near 52-week high / Siri AI performance expectations from iOS27 beta (news headline)

Apple AI and iPhone demand expectations are working positively for the global IT sector.

What signal do crypto and ETF flows send to the market? (Source: signal bundle)

Bitcoin ETF net inflow: 714.7 million dollars / daily inflows around 1 billion dollars (news headline)

Crypto ETF money does not directly push the KOSPI higher, but it supports risk-on sentiment.

So, up or down

Downside risks: US rates and oil variables, (no indicators), persistent uncertainty could trigger volatility

Downside risks: HBM earnings and orders uncertain, Y씨 and D아이 surged, earnings verification needed

Downside risks: weakness in energy and staples, mixed US sectors, potential foreign selling

Supportive factors: US IT and semiconductor strength, +5.74%, reflecting demand expectations

Supportive factors: Apple near 52-week high and AI hopes, technology momentum

Supportive factors: large Bitcoin ETF inflows, 714.7 million dollars, sustaining risk appetite

This is for reference only.

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※ This article is for information purposes and is not investment advice.

※ Investment decisions and responsibility rest with the investor.

※ Figures are as of the time of writing and may change.